Measuring startup watts/amps

[TX63CONV]

Looking to install a small window unit in my garage which would be powered by a generator. On the HD website, the unit I am looking at shows 8amps at 115 volts--less than 1000 watts. I am assuming this is continuous and not at start up which would be higher.

Any way to get that information other than call manufacturer?

 

[pattenp]

Use an AC line splitter with a clamp on amp meter.

 

[BD1]

Does the unit have a nameplate on it ?

 

[sberry]

All the math is still speculation, there is no real substitute for trying the thing. I wouldnt mind knowing if an EU2000 will start that.

 

[nehog]

To answer the OP's question, you need a peak holding amp meter. This type of meter will register the highest current draw, and hold that reading till you clear it.

 

[justsam]

Lacking a meter with MIN/MAX or PEAK hold, you can just take a SWAG and use 5x running current.

 

[wyliesdiesels]

I dont think meters that only have peak and hold functionality accurately capture the in-rush current.

U need to use a meter with in-rush current measuring capability.

My fluke 381 has an in-rush button.

http://en-us.fluke.com/training/tra...rs/how-and-why-to-measure-inrush-current.html

Only meters that offer an inrush button can measure inrush current.

 

[zmaxmotorsports]

Find the feed for the circuit inside the panel and check it with a clamp on meter.

 

[Syberia]

If you can peer inside the unit, it might be listed on the compressor. It might be listed as locked rotor current. My window a/c that draws 12 amps running pulls 50 on startup. A small generator will not be able to do that.

 

[ddawg16]

As Wy pointed out, you are going to have trouble measuring that start up.

What complicates the issue is the source wiring and the unit itself.

When you start something up with a large in rush, several things happen. One of them is voltage drop in the supply wires. That voltage drop reduces the current to the load....and then the load goes into a lower load demand....or, in layman's terms....it groans until it gets going.....or the breaker trips.

Now....if you change things around to where the supply wires are over sized and capable of supplying plenty of power without any real voltage drop....then you might trip that breaker.

Cliff Note version.....try it.

 

[TX63CONV]

I don't have the window unit yet but I see lots of guys at the track running window units off Honda eu2000s in their trailers.

I don't have the generator either and have been leaning toward the champion version.

I guess I could buy the generator and test it with my crappy portable AC that probably has less efficient specs.

5000 watts on startup? Seems like a lot.

 

[Cypherian]

You may want to ask the other guys if they are running a soft start for the AC they have them for RV AC units. I found this as a reference but you will have to check perhaps call the manufacturer of the A/C unit you want to use they may even have the kit . http://www.amazon.com/dp/B000LDPI26/?tag=atomicindus08-20

Cypher

 

[tmcahren]

I would shy away from the Champion unit. It is loud compared to the Honda and use quite a bit more gas. I can run a 7k AC unit with my Honda with the Eco throttle turned off. First I put it in fan mode and get that up and running and then turn the AC on. No issues.

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[TX63CONV]

Tmcahren
Do you know the specs of your AC? Model #?

I hear you on the Honda and would lean that way except it's double the price. Champion has good reviews and the decibel rating is the same (take all of that with a grain of salt).

 

[zmaxmotorsports]

If you can peer inside the unit, it might be listed on the compressor. It might be listed as locked rotor current. My window a/c that draws 12 amps running pulls 50 on startup. A small generator will not be able to do that.

Thats what your start cap is for,How big is the unit/whats the voltage?

 

[Falcon67]

I would shy away from the Champion unit. It is loud compared to the Honda and use quite a bit more gas. I can run a 7k AC unit with my Honda with the Eco throttle turned off. First I put it in fan mode and get that up and running and then turn the AC on. No issues.

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I tested our Champion 3500 using both AC window units in the shop - one 10.5K Samsung and one 8K LG. Ran cords, started the genset, switched on the AC units - both. No problems. The roof AC on the box trailer pulls 21A in 100F weather running full blast. We can run it about 6-ish hours before I feel the need to fuel the generator. Yes, it's louder than a Honda - and it doesn't cost $$$$ either. We've got $380 in ours and it's going into 3rd season. I could buy one every 5 years and still not spend what one Honda costs at the same output. Also, the Champ will quiet down after several uses. Ours is rated around 60dB, it was more like 72dB new. It's noticeably quieter now thought I have not measured it.

Also on noise - "I see lots of guys at the track" - have somebody park next to you with a motor home and a 4K or 7.5K Onan and see if you care how loud your own generator is. Loud is for campgrounds. At the track, the bulk for the open trailer or small box trailer people are PepBoys or Harbor Freight 5000~6500K units and they are all loud as hell.

If you've got the budget for a Honda, they are nice. If not and it's for the track, don't sweat it. Buy more horsepower or entry fees with the money.

 

[sberry]

I don't have the window unit yet but I see lots of guys at the track running window units off Honda eu2000s in their trailers.

I can run a 7k AC unit with my Honda with the Eco throttle turned off.

This is what I wanted to know

 

[TX63CONV]

Would it be safe to speculate that a 5000btu AC can be run on a 15amp breaker and therefor the max watts would be 1725?

I am sure I am over simplifying.

 

[TX63CONV]

I tested our Champion 3500 using both AC window units in the shop - one 10.5K Samsung and one 8K LG. Ran cords, started the genset, switched on the AC units - both. No problems. The roof AC on the box trailer pulls 21A in 100F weather running full blast. We can run it about 6-ish hours before I feel the need to fuel the generator. Yes, it's louder than a Honda - and it doesn't cost $$$$ either. We've got $380 in ours and it's going into 3rd season. I could buy one every 5 years and still not spend what one Honda costs at the same output. Also, the Champ will quiet down after several uses. Ours is rated around 60dB, it was more like 72dB new. It's noticeably quieter now thought I have not measured it.

Also on noise - "I see lots of guys at the track" - have somebody park next to you with a motor home and a 4K or 7.5K Onan and see if you care how loud your own generator is. Loud is for campgrounds. At the track, the bulk for the open trailer or small box trailer people are PepBoys or Harbor Freight 5000~6500K units and they are all loud as hell.

If you've got the budget for a Honda, they are nice. If not and it's for the track, don't sweat it. Buy more horsepower or entry fees with the money.

I hear you. Previously I have had shore power and been able to plug my portable AC in and run without a generator but headed to some new tracks this year and want to be prepared.

 

[Syberia]

Thats what your start cap is for,How big is the unit/whats the voltage?

12000 btu, 120 volts

 

[Syberia]

Would it be safe to speculate that a 5000btu AC can be run on a 15amp breaker and therefor the max watts would be 1725?

I am sure I am over simplifying.

Running watts, you'd be correct. But when the compressor first turns on, for a couple of cycles (we're talking fractions of a second), the amp draw will be much higher until it gets up to speed. A 15 amp breaker will not immediately trip, and in fact is designed to deal with this, so that's why the breaker holds. A generator whose motor isn't powerful enough to keep up with the load, though, will stall.

 

[TX63CONV]

Running watts, you'd be correct. But when the compressor first turns on, for a couple of cycles (we're talking fractions of a second), the amp draw will be much higher until it gets up to speed. A 15 amp breaker will not immediately trip, and in fact is designed to deal with this, so that's why the breaker holds. A generator whose motor isn't powerful enough to keep up with the load, though, will stall.

Ahh....makes sense.

 

[sberry]

You really don't need to know all the math here, you need to know if it works and that may not always match up. As someone said,,, swag.
I have a Weldanpower 210, 6000 watt, an old one. It will start a 5 hp motor. Sposed to be about 1/2 that.

 

[Pwrgeek]

All the math is still speculation, there is no real substitute for trying the thing. I wouldnt mind knowing if an EU2000 will start that.

From trial and error I can tell you.

1 EU 2000 will start any 8000 BTU window unit I've ever tried (probably 10 different ones in all)

1 EU 2000 will start most 13500 BTU window / RV AC units but not some (probably 75% success rate)

1 EU 2000 will not start a 15000 BTU RV AC unit (tried several)

2 EU 2000s in parallel will start and run two 15000 BTU RV AC units as long as you set the thermostats to run so that they don't cycle. If they cycle at some point they will both come on at times too close together and then everyone's SOL until someone gets up and restarts both generators (that's usually me and not my dad... He has more tolerance for heat than I do).

Never tried anything larger than 15000 BTU they make 18000 units for RVs but I don't know anyone that has one.

All of this is at sea level. Go to altitude and your results will vary.


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[sberry]

I was looking at 8k, great to know someone has tested this.

 

[TX63CONV]

Thanks Pwr geek. Probably pulling the trigger on a champion 2000 genset today....I figure I can test various AC from HD or wallyworld before pulling the trigger